<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" type="text/css" href="css/normalize.css">
    <style>
        .wrap {
            width:300px;
            height:300px;
            background-color: pink;
        }
        .box{
            width:300px;
            height:300px;
            background:url(imgs/aaa.jpeg) no-repeat;
            /* background-size:200px 200px; */
            /* background-size:50%; */
            /* background-size: cover; */
            background-size:contain;

        }

        .img2{
            width:50px;
            height:50px;
            background:url(imgs/img50.png) no-repeat;
        }

        .img3 {
            width:50px;
            height:50px;
            background:url(imgs/img100.png) no-repeat;
            background-size:50px 50px;
        }
    </style>
</head>
<body>
    <!-- <div class="wrap"> -->
        <div class="box">
        
        </div>
    <!-- </div> -->

    <div class="img2">
        
    </div>

    <div class="img3"></div>
    
</body>
</html>